Waste and Biomass Valorization最新文献

Anaerobic digestate, a nutrient rich by-product of the biogas industry, is frequently applied to agricultural land as a fertiliser. However, nitrogen losses from its application negatively impact air and water quality. Therefore, methods are needed to reduce these losses. The aim of this study was to test the efficacy of applying digestate with glycerol, an organic carbon rich by-product of the biodiesel industry, on microbial nitrogen immobilisation and the soil microbial community. Soil was incubated with digestate, applied at a rate equivalent to 250 kg-N ha^-1, in a laboratory experiment over 50 days with glycerol additions at either 0, 12, 24 or 36 kg-C m³ of digestate. The addition of glycerol resulted in significantly higher microbial biomass carbon and increased the relative abundance of Gram-negative bacteria. The 24 and 36 kg-C m³ doses of glycerol resulted in similarly greater and longer lasting effect on microbial biomass carbon, indicating that beyond 24 kg-C m³ digestate that nitrogen (or other essential nutrients) became the limiting factor for microbial growth instead of carbon. Soil available nitrogen decreased throughout the study and remained at lower concentrations in glycerol treatments than the digestate only treatment by the end of the study. These results demonstrate that glycerol has the potential to reduce nitrogen losses from digestate application by immobilising nitrogen in the microbial biomass. Therefore, the co-application of digestate and glycerol to soil is a potential mechanism for the biogas and biofuel industries to valorise their respective by-products. Further research is needed to verify that this method is viable under field conditions.

Refuse-derived fuel (RDF) produced from the processing of municipal solid waste (MSW) has a high content of biomass and plastics. Pyrolysis of RDF produces a bio-oil which is highly oxygenated, viscous, acidic with a high moisture content and unsuitable for direct use in conventional combustion systems and consequently requires upgrading. A novel process of pyrolysis with non-thermal plasma/catalysis has been developed to produce de-oxygenated bio-oils and gases from RDF. The volatiles from the pyrolysis stage are passed directly to a non-thermal plasma/catalytic reactor where upgrading of the pyrolysis volatiles takes place. Detailed analysis of the product oils and gases is presented in relation to process conditions and in the presence of different catalysts (TiO₂, MCM-41, ZSM-5, and Al₂O₃). Even in the absence of a catalyst, the presence of the non-thermal plasma resulted in high yields of CO and CO₂ gases and reduced bio-oil oxygen content, confirming deoxygenation of the RDF pyrolysis volatiles. The addition of catalysts MCM-41 and ZSM-5 generated the highest yields of CO, CO₂, and H₂ due to the synergy between catalyst and plasma. The catalysts ranked in terms of total oxygenated oil yield are as follows: MCM-41 < ZSM-5 < TiO₂ < Al₂O₃. Pyrolysis of RDF produces an oil containing oxygenated species from biomass and hydrocarbon species from plastics. The non-thermal plasma generates high energy electrons which generate radicals and intermediates from the pyrolysis volatiles which synergistically interact with the catalysts to enable deoxygenation of the oxygenated hydrocarbons through decarboxylation and decarbonylation reactions.

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